PALEOFLOOD DISCHARGE ANALYSIS OF LATE WISCONSINAN JõKUHLHAUPS, MENTASTA PASS VALLEY, NORTHEASTERN ALASKA RANGE, USING MODERN ENGINEERING THEORY

Physiographic and stratigraphic evidence indicates that during flood-surge events meltwater from Glacial Lake Atna periodically poured through the lower Slana River valley and entered the upper Tok River during the last major (Donnelly) glaciation. Paleoflood levels were interpreted on aerial photographs and IfSAR (Interferometric Synthetic Aperture Radar) imagery. Using a digital elevation model, ArcGIS and Grapher generated topographic profiles, and engineering parameters were derived to estimate paleoflood discharges and open-channel flow velocities for flood elevations ranging from 673-761 m (relative to North American Vertical Datum of 1988), using Manning’s equation. Manning’s equation calculations indicated paleoflood discharge and open-channel velocity values were between ~ 4.3-7.5 x 10⁶ m³/s and ~ 32-37 m/s respectively. Froude numbers were calculated, and results indicate values ranging from 1.15 and 1.18, classifying the flow as supercritical.